$\begingroup$I noticed that your question has a few answers available and has been open for a while, just curious if any of the available answers was able to help. If not, then what questions do you still have?$\endgroup$
– tbm0115Jul 3 '16 at 20:17

$\begingroup$Both answers deal with printing the actual circuits, while the question is about printing masks on common PCBs which would then be corroded. Maybe I need to rephrase my question to make this clearer?$\endgroup$
– Ronan PaixãoJul 19 '16 at 13:07

$\begingroup$Yeah, that would help. I don't think you need to reword your question, but maybe just add that note. Also it looks like @TextGeek mentioned masking in a comment that might help.$\endgroup$
– tbm0115Jul 19 '16 at 14:38

$\begingroup$Is there a reason you cannot use photoreactive copper boards and expose them to light with a printed transparency? Desktop laser jet printers can usually print directly onto transparencies to generate photomasks. These can produce quite detailed circuitry but you may need to check the specifics.$\endgroup$
– TafTMar 13 '17 at 8:56

2 Answers
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In addition to the thermal issues Tormod raised, there is a conductivity issue. Present conductive filaments are much less conductive than copper. The power loss may be enough to affect functionality. Also, the lost power goes to heat, making the thermal problems worse.

Printing itself significantly raises resistivity. Proto-pasta claims 30 ohm-cm along X and Y, 115 along Z. More intuitively, each cm of length of a 2.5mm wide printed trace, 0.4mm thick, should add several hundred ohms with the Proto-pasta, or several tens of ohms with the F-electric. That may be enough to matter.

$\begingroup$I imagine pre-calculating the resistance of a printed conductor can be a science in itself, meaning it could be difficult to use protopasta for anything complicated!$\endgroup$
– Tormod HaugeneJan 22 '16 at 22:04

$\begingroup$@TormodHaugene, that's surely true. I just approximated by cross-sectional area and length, which should be in the ballpark. But layer height, ratio of nozzle to layer height, and many other things surely matter, too.$\endgroup$
– TextGeekJan 26 '16 at 14:59

$\begingroup$Question is about printing masks, not about printing circuits directly. This is a good answer about printing circuits but not about printing masks. -1$\endgroup$
– TafTMar 13 '17 at 8:53

In theory, I imagine you can, but there are some practical considerations that might need some thought:

If you have a desktop printer with multiple extruders, you could probably print with both one conductive and one structural filament, and thereby build circuits in 3D.

One concern would be the low melting points of most 3D printed filaments, since one would have to limit the heat generated by the mounted components and connections so that the structure of the "board" would not be melted.

Mounting components to the board would also differ from a normal PCB, since you would have to connect the components with the conductive filament without melting the structure of the board. In other words, you probably would have to use conductive filament as "solder", and melt components into place.

Whether you could use typical tools used for mounting SMD components with conductive filament as solder is beyond my knowledge.

$\begingroup$I do not intend to print the whole board from scratch with conductive filament, but to print a filament mask above a standard PCB. The mask would (if possible) allow corrosion of the PCB copper by standard PCB-making process, leaving the copper tracks where the masks protects them. I'm concerned about if the mask would stick and if it allows fine tracks needed for SMD components.$\endgroup$
– Ronan PaixãoJan 19 '16 at 15:50

2

$\begingroup$Ahh, sorry, hadn't realized that's what you meant. There's a report of someone using NinjaFlex filament as mask on standard PCBs, which says it adheres well to the copper, unlike some other filaments. 3dprint.com/11367/3d-print-copper-circuit-board Or one could substitute a laser cutter for the extruder head, and subtract copper directly... :)$\endgroup$
– TextGeekJan 22 '16 at 20:47